The present invention relates to a brake system for automotive vehicles including a controllable pneumatic brake power booster and a master brake cylinder, wherein a control valve of the brake power booster is operable by an actuating pedal, on the one hand, and is actuatable by a solenoid irrespective of the driver's wish, on the other hand, including an arrangement for determining the actuating force applied to the actuating pedal, and an electronic controller having control signals which are used to activate the solenoid.
In a combined actuation of the brake power booster by independent activation and by the actuating force applied to the actuating pedal, it is necessary to know about the actuating force in some possible applications, for example, in driving stability control operations.
German patent No. 33 25 854 discloses a brake controller for controlling a vehicle brake system which interacts with a brake power booster that is activatable irrespective of the driver's wish, preferably electrically. The mentioned electric activation is done by way of a control valve which is arranged outside the brake power booster and takes effect on a pneumatic differential pressure adapted to be introduced in the booster housing. The control valve is furnished with control signals of a data processing system which processes, as input quantities, signals from two sensor assemblies. The first sensor assembly includes a speed sensor having signals which are differentiated to determine the vehicle deceleration. The second sensor assembly is a force sensor which is used to determine the actuating force applied to the actuating pedal. The data processing system has static characteristic curves from which nominal deceleration values are derived.
A disadvantage of the prior art controller is the use of the force sensor for determining the above mentioned actuating force. The force sensor must be installed in the actuating rod of the brake power booster. Installation of the force sensor requires sophisticated structure, on the one hand, and involves problems, on the other hand, which are due to a limited mounting space.
Therefore, an object of the present invention is to provide measures which permit indirectly determining the actuating force that acts upon the actuating pedal.